1. Field of the Invention
The present invention relates to the multiple access technologies and the wireless technologies utilizing the multiple access technology, and it particularly relates to a multiple access method and a radio apparatus utilizing the multiple access method in order to multiple-connect a plurality of terminal apparatuses by partitioning the space.
2. Description of the Related Art
In wireless communication, multiple access technologies are being used in order to realize effective use of frequency resources. Such multiple access technologies include FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access). In recent years, the widespread use of cellular phones and other circumstances are adding demands for even higher efficiency in the use of radio frequencies. And as one way of solving this problem, new multiple access technologies, which include SDMA (Space Division Multiple Access) and PDMA (Path Division Multiple Access), are now being investigated.
In SDMA, for example, a time slot for the same frequency is divided into a plurality of spatial divisions at a radio base station apparatus, and data transmission is performed with user terminals to which the divided spaces are allocated. The signals to be used by the respective user terminals are generally separated by a mutual interference eliminating means, such as an adaptive array antenna, installed at the radio base station apparatus (see, for example, the Relate Art List (1) below). The adaptive array antenna synthesizes signals received by a plurality of antennas by weighting them with weight vectors according to their respective propagation environments before outputting signals on a desired user terminal.